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    <h1 id="计算机网络概述"><a class="markdownIt-Anchor" href="#计算机网络概述"></a> 计算机网络概述</h1>
<p>整理：白开画</p>
<span id="more"></span>
<h2 id="计算机网络的基本概念"><a class="markdownIt-Anchor" href="#计算机网络的基本概念"></a> 计算机网络的基本概念</h2>
<p>计算机网络是<strong>通信技术</strong>与<strong>计算机技术</strong>紧密结合的产物。</p>
<p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">计</mi><mi mathvariant="normal">算</mi><mi mathvariant="normal">机</mi><mi mathvariant="normal">网</mi><mi mathvariant="normal">络</mi><mo>=</mo><mi mathvariant="normal">通</mi><mi mathvariant="normal">信</mi><mi mathvariant="normal">技</mi><mi mathvariant="normal">术</mi><mo>+</mo><mi mathvariant="normal">计</mi><mi mathvariant="normal">算</mi><mi mathvariant="normal">机</mi><mi mathvariant="normal">技</mi><mi mathvariant="normal">术</mi></mrow><annotation encoding="application/x-tex">计算机网络=通信技术+计算机技术
</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.36687em;vertical-align:0em;"></span><span class="mord cjk_fallback">计</span><span class="mord cjk_fallback">算</span><span class="mord cjk_fallback">机</span><span class="mord cjk_fallback">网</span><span class="mord cjk_fallback">络</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.66666em;vertical-align:-0.08333em;"></span><span class="mord cjk_fallback">通</span><span class="mord cjk_fallback">信</span><span class="mord cjk_fallback">技</span><span class="mord cjk_fallback">术</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">+</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0em;vertical-align:0em;"></span><span class="mord cjk_fallback">计</span><span class="mord cjk_fallback">算</span><span class="mord cjk_fallback">机</span><span class="mord cjk_fallback">技</span><span class="mord cjk_fallback">术</span></span></span></span></span></p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806180427.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806180427.png" class="lozad post-image"></p>
<h3 id="什么是计算机网络"><a class="markdownIt-Anchor" href="#什么是计算机网络"></a> 什么是计算机网络？</h3>
<ul>
<li>
<p>定义：计算机网络是<strong>互联</strong>的、<strong>自治</strong>的计算机集合。</p>
<p><strong>自治</strong>-无主从关系</p>
<p><strong>互联</strong>-互联互通</p>
</li>
<li>
<p>通过<strong>交换网络</strong>互联的主机</p>
</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806180918.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806180918.png" class="lozad post-image"></p>
<h3 id="什么是lnternet"><a class="markdownIt-Anchor" href="#什么是lnternet"></a> 什么是lnternet？</h3>
<p>​	lnternet结构：端系统通过接入ISP连接到Internet</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806190741.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806190741.png" class="lozad post-image"></p>
<p>在网络中心：少数互联的大型网络</p>
<ul>
<li>“一级”商业ISPs（如：网通、电信、Sprint、AT&amp;T），提供国家或国际范围的覆盖</li>
<li>内容提供商网络（如：Google）：私有网络，连接其数据中心与lnternet，通常绕过一级ISP和区域ISPs</li>
</ul>
<h4 id="组成细节"><a class="markdownIt-Anchor" href="#组成细节"></a> 组成细节</h4>
<ul>
<li>全球最大的<strong>互联网络</strong></li>
<li>ISP网络互联的“<strong>网络之网络</strong>”</li>
<li>通过<strong>通信线路</strong>连接（光纤、铜缆、无线电、卫星等）</li>
<li><strong>分组交换</strong>：转发分组（路由器和交换机）</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806181653.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806181653.png" class="lozad post-image"></p>
<h4 id="服务角度"><a class="markdownIt-Anchor" href="#服务角度"></a> 服务角度</h4>
<ul>
<li><strong>为网络应用提供通信服务的通信基础设施</strong>（web、VoIP、Email、网络游戏、电子商务、社交网络）</li>
<li>为网络应用提供应用编程接口（API）</li>
</ul>
<h2 id="网络协议"><a class="markdownIt-Anchor" href="#网络协议"></a> 网络协议</h2>
<h3 id="什么是网络协议"><a class="markdownIt-Anchor" href="#什么是网络协议"></a> 什么是网络协议？</h3>
<p>​	网络协议，简称协议，是为进行网络中的数据交换而建立的规则、标准或约定</p>
<p>​	<strong>协议</strong>规定了通信实体之间所交换的消息的<strong>格式、意义、顺序</strong>以及针对收到消息或发生的事件所采取的“<strong>动作</strong>”</p>
<p>​	协议规范了所有的发送和接收过程</p>
<h3 id="协议三要素"><a class="markdownIt-Anchor" href="#协议三要素"></a> 协议三要素</h3>
<p>1.<strong>语法</strong></p>
<ul>
<li>数据与控制信息的结构或格式</li>
<li>信号电平</li>
</ul>
<p>2.<strong>语义</strong></p>
<ul>
<li>需要发出任何控制信息</li>
<li>完成何种动作以及做出何种响应</li>
<li>差错控制</li>
</ul>
<p>3.<strong>时序</strong></p>
<ul>
<li>事件顺序</li>
<li>速度匹配</li>
</ul>
<h2 id="计算机网络结构"><a class="markdownIt-Anchor" href="#计算机网络结构"></a> 计算机网络结构</h2>
<p>网络边缘：主机、网络应用</p>
<p>接入网络，物理介质：有线或无线通信链路</p>
<p>网络核心（核心网络）：互联的路由器（或分组转发设备）、网络之网络</p>
<h3 id="网络边缘"><a class="markdownIt-Anchor" href="#网络边缘"></a> 网络边缘</h3>
<p>1.主机（端系统）</p>
<ul>
<li>位于“网络边缘”</li>
<li>运行网络应用程序（web、Email）</li>
</ul>
<p>2.客户/服务器应用模型</p>
<ul>
<li>客户发送请求，接受服务器响应（web应用，文件传输ftp应用）</li>
</ul>
<p>3.对等（p2p）应用模型</p>
<ul>
<li>无专用服务器</li>
<li>通信在对等实体之间直接通信</li>
</ul>
<h3 id="接入网络"><a class="markdownIt-Anchor" href="#接入网络"></a> 接入网络</h3>
<p>1.类型</p>
<ul>
<li>住宅（家庭）接入网络</li>
<li>机构接入网络（学校，企业）</li>
<li>移动接入网络</li>
</ul>
<p>2.数字用户线路（DSL）</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806182025.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806182025.png" class="lozad post-image"></p>
<p>特点：</p>
<p>1.利用已有的电话线连接中心局的DSLAM</p>
<ul>
<li>数据通信通过DSL电话线接入网络</li>
<li>语音（电话）通过DSL电话线接入电话网络</li>
</ul>
<p>2.&lt;2.5Mbps上行传输速率（典型速率&lt;1Mbps)</p>
<p>3.&lt;24Mbps下行传输速率（典型速率&lt;10Mbps）</p>
<p>4.FDM（频分多路复用）：&gt;50kHz-1MHz用于下行、4kHz-50kHz用于上行、0kHz-4kHz用于传统电话</p>
<p>3.电缆网络</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806183308.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806183308.png" class="lozad post-image"></p>
<p>频分多路复用（FDM）：在不同频带（载波）上传输不同频道</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806183541.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806183541.png" class="lozad post-image"></p>
<p>HFC:混合光纤同轴电缆</p>
<ul>
<li>非对称：下行高达30Mbps传输速率，上行为2Mbps传输速率</li>
</ul>
<p>各家庭（设备）通过电缆网络-&gt;光纤接入ISP路由器</p>
<ul>
<li>各家庭共享家庭至电缆端的接入网络</li>
<li>不同于DSL的独占至中心局的接入</li>
</ul>
<p>4.典型的家庭网络的接入：</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184401.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184401.png" class="lozad post-image"></p>
<p>5.机构（企业）接入网络：</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184619.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184619.png" class="lozad post-image"></p>
<p>6.无线接入网络</p>
<p>​	通过共享的无线接入网络连接系统与路由器</p>
<p>无线局域网（LANs）：</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184949.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806184949.png" class="lozad post-image"></p>
<ul>
<li>同一建筑内</li>
<li>802.11b/g（wifi）：11Mbps-54Mbps传输速率</li>
</ul>
<p>广域网无线接入：</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806185206.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806185206.png" class="lozad post-image"></p>
<ul>
<li>通过电信运营商（蜂窝网），接入范围几十公里</li>
<li>带宽：1Mbps、10Mbps、100Mbps</li>
</ul>
<h3 id="网络核心"><a class="markdownIt-Anchor" href="#网络核心"></a> 网络核心</h3>
<p>​	网络核心的关键功能：<strong>路由</strong>+<strong>转发</strong></p>
<ul>
<li>
<p>路由：确定分组从源到目的传输路径</p>
</li>
<li>
<p>转发：将分组从路由器的输入端口交换至正确的输出端口</p>
</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806185749.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210806185749.png" class="lozad post-image"></p>
<h4 id="电路交换"><a class="markdownIt-Anchor" href="#电路交换"></a> 电路交换</h4>
<p>1.最典型的电路交换网络：电话网络</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811205951.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811205951.png" class="lozad post-image"></p>
<p>2.电路交换三个阶段：</p>
<ol>
<li>建立连接（呼叫/电路建立）</li>
<li>通信</li>
<li>释放连接（拆除电路）</li>
</ol>
<p>3.特点：独占资源</p>
<h5 id="多路复用"><a class="markdownIt-Anchor" href="#多路复用"></a> 多路复用</h5>
<p>特点：链路/网络资源划分为“资源片”</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811210619.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811210619.png" class="lozad post-image"></p>
<p>典型的多路复用方法：</p>
<ul>
<li>频分多路复用（FDM）</li>
<li>时分多路复用（TDM）</li>
<li>波分多路复用（WDM）</li>
<li>码分多路复用（CDM）</li>
</ul>
<p>1.频分多路复用FDM</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811211242.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811211242.png" class="lozad post-image"></p>
<p>​	频分多路复用的各个用户占不同的带宽资源（这里的“带宽”是频率带宽（单位：Hz）而不是数据的发射频率）</p>
<p>​	用户在分配到一定频带后，在通信过程中始终都占用这个频带</p>
<p>2.时分多路复用TDM</p>
<p>​	时分复用是将时间划分为一段段等长的时分复用帧（TDM帧），每一个用户在TDM帧中占用固定序号的时隙</p>
<p>​	每用户所占用的时隙是周期性出现（其周期就是TDM帧的长度）</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811212415.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811212415.png" class="lozad post-image"></p>
<p>​	时分复用的所有用户是在不同时间占用相同的频带宽度</p>
<p>3.波分多路复用WDM</p>
<p>​	波分复用就是光的频分复用</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811212848.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811212848.png" class="lozad post-image"></p>
<p>4.码分多路复用CDM</p>
<p>​	广泛应用于无线链路共享（如蜂窝网，卫星通信等）</p>
<p>​	每一个用户分配一个唯一的m bit码片序列，其中“0”用“-1”表示，“1”用“+1”表示，例如s站的码片序列：（-1-1-1+1+1-1+1+1）</p>
<p>​	各用户使用相同频率载波，利用各自码片序列编码数据</p>
<p>​	编码信号=原始数据*码片序列</p>
<ul>
<li>
<p>如发送比特1（+1），则发送自己的m bit码片序列</p>
</li>
<li>
<p>如发送比特0（-1），则发送该码片序列的m bit码片序列的反码</p>
</li>
<li>
<p>各用户码片序列相互正交</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811214208.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811214208.png" class="lozad post-image"></p>
</li>
</ul>
<h3 id="报文交换与分组交换"><a class="markdownIt-Anchor" href="#报文交换与分组交换"></a> 报文交换与分组交换</h3>
<p>​	1.报文：原（应用）发送信息整体（应用如：电报）</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215047.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215047.png" class="lozad post-image"></p>
<p>​	2.分组：报文拆分出来的一系列相对较小的数据包</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215259.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215259.png" class="lozad post-image"></p>
<p>​	分组交换需要报文的拆分与重组，会产生额外的时间开销</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215616.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215616.png" class="lozad post-image"></p>
<p>3.分组交换：统计多路复用</p>
<p>​	按需共享链路</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215742.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811215742.png" class="lozad post-image"></p>
<p>4.存储-转发</p>
<p>​	报文交换与分组交换均采取存储-转发交换方式</p>
<p>​	区别：</p>
<ul>
<li>报文交换以完整报文进行“存储-转发”</li>
<li>分组交换以较小和分进行“存储-转发”</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811220204.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210811220204.png" class="lozad post-image"></p>
<p>5.分组交换：传输延迟</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812103803.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812103803.png" class="lozad post-image"></p>
<p>​	L：比特长度	R：链路传输速率</p>
<p>​	报文交换：</p>
<ul>
<li>报文长度为M bits</li>
<li>链路带宽R bps</li>
<li>每次传输报文需要M/R秒</li>
</ul>
<p>​      分组交换：</p>
<ul>
<li>报文被拆分为多个分组</li>
<li>分组长度为L bits</li>
<li>每个分组传输时延为L/R秒</li>
</ul>
<h3 id="分组交换与电路交换"><a class="markdownIt-Anchor" href="#分组交换与电路交换"></a> 分组交换与电路交换</h3>
<p>​	适用于突发数据传输网络</p>
<ul>
<li>资源充分共享</li>
<li>简单、无需呼叫建立</li>
</ul>
<p>​    可能产生拥塞：分组延迟和丢失</p>
<ul>
<li>需要协议处理可靠数据传输和拥塞控制</li>
</ul>
<h2 id="计算机网络性能"><a class="markdownIt-Anchor" href="#计算机网络性能"></a> 计算机网络性能</h2>
<h3 id="速率"><a class="markdownIt-Anchor" href="#速率"></a> 速率</h3>
<p>速率即数据率或数据传输速率或比特率</p>
<ul>
<li>单位时间（秒）传输信息（比特）量</li>
<li>计算机网络中最重要的一个性能指标</li>
<li>单位：b/s（或bps）、kb/s、Mb/s、Gb/s</li>
<li>k=10<sup>3、M=10</sup>6、G=10^9</li>
</ul>
<p>​    速率往往是指<strong>额定速率</strong>或<strong>标称速率</strong></p>
<h3 id="带宽"><a class="markdownIt-Anchor" href="#带宽"></a> 带宽</h3>
<p>​	“带宽”原本指信号具有的频率宽度，即最高频率与最低频率之差，单位是赫兹（Hz）</p>
<p>​	网络的“带宽”通常是数字信道所能传输的“最高数据率”，单位：b/s（bps）</p>
<p>​	常用的带宽单位：</p>
<ul>
<li>kb/s（10^3 b/s）</li>
<li>Mb/s（10^6 b/s）</li>
<li>Gb/s（10^9 b/s）</li>
<li>Tb/s（10^12 b/s）</li>
</ul>
<h3 id="延迟时延"><a class="markdownIt-Anchor" href="#延迟时延"></a> 延迟/时延</h3>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812114339.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812114339.png" class="lozad post-image"></p>
<p>4种分组延迟:</p>
<p>​	1.结点处理延迟：</p>
<ul>
<li>差错检测</li>
<li>确定输出链路</li>
<li>通常&lt;msec</li>
</ul>
<p>​    2.排队延迟：</p>
<ul>
<li>等待输出链路可用</li>
<li>取决于路由器拥塞程度</li>
</ul>
<p>​    3.传输延迟：</p>
<ul>
<li>L：分组长度（bits）</li>
<li>R：链路带宽（bps）</li>
<li>d=L/R</li>
</ul>
<p>​    4.传播延迟：</p>
<ul>
<li>d：物理链长度</li>
<li>s：传播速度（~2×10^8 m/sec）</li>
<li>d=d/s</li>
</ul>
<h3 id="时延带宽积"><a class="markdownIt-Anchor" href="#时延带宽积"></a> 时延带宽积</h3>
<p class='katex-block'><span class="katex-display"><span class="katex"><span class="katex-mathml"><math><semantics><mrow><mi mathvariant="normal">时</mi><mi mathvariant="normal">延</mi><mi mathvariant="normal">带</mi><mi mathvariant="normal">宽</mi><mi mathvariant="normal">积</mi><mo>=</mo><mi mathvariant="normal">传</mi><mi mathvariant="normal">播</mi><mi mathvariant="normal">延</mi><mi mathvariant="normal">迟</mi><mo>×</mo><mi mathvariant="normal">带</mi><mi mathvariant="normal">宽</mi><mo>=</mo><mi>d</mi><mo>×</mo><mi>R</mi><mi mathvariant="normal">（</mi><mi>b</mi><mi>i</mi><mi>t</mi><mi>s</mi><mi mathvariant="normal">）</mi></mrow><annotation encoding="application/x-tex">时延带宽积 = 传播延迟 × 带宽 = d×R（bits）
</annotation></semantics></math></span><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.36687em;vertical-align:0em;"></span><span class="mord cjk_fallback">时</span><span class="mord cjk_fallback">延</span><span class="mord cjk_fallback">带</span><span class="mord cjk_fallback">宽</span><span class="mord cjk_fallback">积</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.66666em;vertical-align:-0.08333em;"></span><span class="mord cjk_fallback">传</span><span class="mord cjk_fallback">播</span><span class="mord cjk_fallback">延</span><span class="mord cjk_fallback">迟</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.36687em;vertical-align:0em;"></span><span class="mord cjk_fallback">带</span><span class="mord cjk_fallback">宽</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span><span class="mrel">=</span><span class="mspace" style="margin-right:0.2777777777777778em;"></span></span><span class="base"><span class="strut" style="height:0.77777em;vertical-align:-0.08333em;"></span><span class="mord mathdefault">d</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span><span class="mbin">×</span><span class="mspace" style="margin-right:0.2222222222222222em;"></span></span><span class="base"><span class="strut" style="height:0.69444em;vertical-align:0em;"></span><span class="mord mathdefault" style="margin-right:0.00773em;">R</span><span class="mord cjk_fallback">（</span><span class="mord mathdefault">b</span><span class="mord mathdefault">i</span><span class="mord mathdefault">t</span><span class="mord mathdefault">s</span><span class="mord cjk_fallback">）</span></span></span></span></span></p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812115750.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812115750.png" class="lozad post-image"></p>
<p>​	链路的时延带宽积又称以比特为单位的链路长度，时延带宽积为长度单位</p>
<h3 id="分组丢失丢包"><a class="markdownIt-Anchor" href="#分组丢失丢包"></a> 分组丢失（丢包）</h3>
<p>​	原因：</p>
<ul>
<li>队列缓存容量有限</li>
<li>分组到达已满队列将被丢弃</li>
</ul>
<p>​      丢弃分组可能由前序结点或源重发（也可能不重发）</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812120702.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812120702.png" class="lozad post-image"></p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812120732.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812120732.png" class="lozad post-image"></p>
<h3 id="吞吐量率"><a class="markdownIt-Anchor" href="#吞吐量率"></a> 吞吐量/率</h3>
<p>​	吞吐量：表示在发送端与接收端之间传送数据速率（b/s）</p>
<ul>
<li>即时吞吐量：给定时刻的速率</li>
<li>平均吞吐量：一段时间的平均速率</li>
</ul>
<p>​    瓶颈链路：端到端路径上，限制端到端吞吐量的链路</p>
<h2 id="计算机网络体系结构"><a class="markdownIt-Anchor" href="#计算机网络体系结构"></a> 计算机网络体系结构</h2>
<p>​	计算机网络体系结构是从<strong>功能上</strong>描述计算机网络结构</p>
<p>​	计算机网络体系结构简称网络体系结构是<strong>分层结构</strong></p>
<p>​	每层遵循某个/些<strong>网络协议</strong>完成本层功能</p>
<p>​	<strong>计算机网络体系结构</strong>是计算机网络的各层及其协议的集合</p>
<p>​	体系结构是一个计算机网络的功能层次及其关系的<strong>定义</strong></p>
<p>​	体系结构是<strong>抽象的</strong></p>
<p>分层结构的优点：</p>
<p>​	1.结构清晰，有利于识别复杂系统的部件及其关系</p>
<ul>
<li>分层的<strong>参考模型</strong></li>
</ul>
<p>​    2.模块化的分层已于系统<strong>更新、维护</strong></p>
<ul>
<li>任何一层服务实现的改变对于系统其它层都是透明的（看不见的、不可见的）</li>
</ul>
<p>​     3.有利于标准化</p>
<h3 id="分层网络体系结构基本概念"><a class="markdownIt-Anchor" href="#分层网络体系结构基本概念"></a> 分层网络体系结构基本概念</h3>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812153631.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812153631.png" class="lozad post-image"></p>
<p>​	1.实体表示任何可发送或接受信息的硬件或软件进程</p>
<p>​	2.协议是控制<strong>两个对等实体</strong>进行通信的规则的集合，协议是“<strong>水平的</strong>”</p>
<p>​	3.任一层实体需要使用<strong>下层</strong>服务，遵循本层协议，实现本层功能，向<strong>上层</strong>提供服务，服务是“<strong>垂直的</strong>”</p>
<p>​	4.下层协议的实现对上层的服务用户是<strong>透明</strong>的（不可见的）</p>
<p>​	5.同系统的相邻层实体间通过<strong>接口</strong>进行交互，通过<strong>服务访问点SAP</strong>，交换<strong>原语</strong>，指定请求的特定服务</p>
<h3 id="osi参考模型"><a class="markdownIt-Anchor" href="#osi参考模型"></a> OSI参考模型</h3>
<p>​	开放系统互联（OSI）参考模型是由国际标准化组织（ISO）于1984年提出的分层网络体系结构模型</p>
<p>​	目的是支持<strong>异构网络系统</strong>的互联互通</p>
<p>​	异构网络模型系统互联的<strong>国际标准</strong></p>
<p>​	理解网络通信模型的最佳<strong>学习工具</strong>（理论模型）</p>
<ul>
<li>理论成功，市场失败</li>
</ul>
<p>​    7层（功能），每层完成特定的网络功能</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812155722.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812155722.png" class="lozad post-image"></p>
<h3 id="osi参考模型解释的通信过程"><a class="markdownIt-Anchor" href="#osi参考模型解释的通信过程"></a> OSI参考模型解释的通信过程</h3>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812160845.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812160845.png" class="lozad post-image"></p>
<h3 id="osi参考模型数据封装与通信过程"><a class="markdownIt-Anchor" href="#osi参考模型数据封装与通信过程"></a> OSI参考模型数据封装与通信过程</h3>
<p>​	通信过程：</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812161417.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812161417.png" class="lozad post-image"></p>
<p>​	数据封装：</p>
<p>​		增加控制单元，结构协议数据单元（PDU）</p>
<p>​		控制信息主要包括：</p>
<ul>
<li>地址：标识发送端/接收端</li>
<li>差错检测编码：用于差错检测或纠错</li>
<li>协议控制：实现协议功能的附加信息，如：优先级、服务质量（QoS）、安全控制等</li>
</ul>
<h3 id="osi非端到端层次的主要功能"><a class="markdownIt-Anchor" href="#osi非端到端层次的主要功能"></a> OSI非端到端层次的主要功能</h3>
<p>​	1.物理层功能</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812162414.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812162414.png" class="lozad post-image"></p>
<ul>
<li>规范接口特性（机械特性、电气特性、功能特性、规模特性）</li>
<li>比特编码</li>
<li>数据率</li>
<li>比特同步（时钟同步）</li>
<li>传输模式（单工（单向传输）、半双工（双向交替通信）、全双工）</li>
</ul>
<p>​    2.数据链路层功能</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812162932.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812162932.png" class="lozad post-image"></p>
<ul>
<li>负责<strong>结点-结点</strong>数据传输</li>
<li>组帧</li>
<li>物理寻址，在帧头中增加发送端和/或接受端的<strong>物理地址</strong>标识数据帧的发送端和/接收端</li>
<li>流量控制，避免淹没接收端</li>
<li>差错控制，检测并重传损坏或丢失帧，并避免重复帧</li>
<li>访问（接入）控制，在任一给定时刻决定哪个设备拥有链路（物理介质）控制使用权</li>
</ul>
<p>​    3.网络层功能</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812164457.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812164457.png" class="lozad post-image"></p>
<ul>
<li>负责<strong>源主机到目的主机</strong>数据分组交付（可能穿越多个网络）</li>
<li><strong>逻辑寻址</strong>，<strong>全局唯一</strong>逻辑地址，确保数据分组被送达目的的主机，如IP地址</li>
<li><strong>路由</strong>，路由器（或网关）互联网络，并路由分组至最终目的主机（路径选择）</li>
<li>分组转发</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812165321.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812165321.png" class="lozad post-image"></p>
<h3 id="osi端到端层次的主要功能"><a class="markdownIt-Anchor" href="#osi端到端层次的主要功能"></a> OSI端到端层次的主要功能</h3>
<p>​	1.传输层</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812165522.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812165522.png" class="lozad post-image"></p>
<ul>
<li>分段与重组</li>
<li>SAP寻址，确保将完整报文提交给正确的<strong>进程</strong>，如端口号</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170327.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170327.png" class="lozad post-image"></p>
<ul>
<li>连接控制</li>
<li>流量控制</li>
<li>差错控制</li>
</ul>
<p>​    2.会话层功能</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170551.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170551.png" class="lozad post-image"></p>
<ul>
<li>对话控制，建立、维护</li>
<li>同步，在数据流中插入“同步点”</li>
<li>最“薄”的一层</li>
</ul>
<p>​     3.表示层功能</p>
<p>​		处理两个系统间交换信息的<strong>语法与语义</strong>问题</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170825.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812170825.png" class="lozad post-image"></p>
<ul>
<li>数据表示转换，转换为主机独立的编码</li>
<li>加密/解密</li>
<li>压缩/解压缩</li>
</ul>
<p>​     4.应用层</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812171215.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812171215.png" class="lozad post-image"></p>
<ul>
<li>支持用户通过用户代理（如浏览器）或网络接口<strong>使用网络（服务）</strong></li>
<li>典型应用层服务：文件传输（FTP）、电子邮件（SMTP）、Web（HTTP）等</li>
</ul>
<h3 id="tcpip参考模型"><a class="markdownIt-Anchor" href="#tcpip参考模型"></a> TCP/IP参考模型</h3>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812171853.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812171853.png" class="lozad post-image"></p>
<h3 id="5层参考模型"><a class="markdownIt-Anchor" href="#5层参考模型"></a> 5层参考模型</h3>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812172142.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812172142.png" class="lozad post-image"></p>
<p>​	综合OSI和TCP/IP的优点</p>
<p>​	1.应用层：支持格网络应用</p>
<ul>
<li>FTP、SMTP、HTTP</li>
</ul>
<p>​     2.传输层：进程-进程的数据传输</p>
<ul>
<li>TCP、UDP</li>
</ul>
<p>​      3.网络层：源主机到目的主机的数据分组路由与转发</p>
<ul>
<li>IP协议、路由协议等</li>
</ul>
<p>​      4.链路层：相邻网络元素（主机、交换机、路由器等）的数据传输</p>
<ul>
<li>以太网、802.11（WiFi）、PPP</li>
</ul>
<p>​       5.物理层：比特传输</p>
<p>​	5层参考模型的数据封装</p>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812173430.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812173430.png" class="lozad post-image"></p>
<h2 id="计算机网络发展历史"><a class="markdownIt-Anchor" href="#计算机网络发展历史"></a> 计算机网络发展历史</h2>
<h3 id="1961-1972早期分组交换原理提出与应用"><a class="markdownIt-Anchor" href="#1961-1972早期分组交换原理提出与应用"></a> 1961-1972：早期分组交换原理提出与应用</h3>
<ul>
<li>1961：Kleinrock-排队论证实分组交换的有效性</li>
<li>1964：Baran-分组交换应用与军事网络</li>
<li>1967：ARPA提出ARPAnet构想</li>
<li>1969：第一个ARPAnet结点运行</li>
<li>1972：ARPAnet公开演示，第一个主机-主机协议NCP，第一个e-mail程序，ARPAnet拥有15个结点</li>
</ul>
<h3 id="1972-1980网络互联大量新型-私有网络的涌现"><a class="markdownIt-Anchor" href="#1972-1980网络互联大量新型-私有网络的涌现"></a> 1972-1980：网络互联，大量新型、私有网络的涌现</h3>
<ul>
<li>1970：在夏威夷构建了ALOHAnet卫星网络</li>
<li>1974：Cerf与Kahn-提出网络互联体系结构</li>
</ul>
<p><img src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812182049.png" alt="" / srcset="data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20viewBox='0%200%20300%20300'%3E%3C/svg%3E" data-src="https://gitee.com/baikaihua/tochang/raw/master/QQ%E6%88%AA%E5%9B%BE20210812182049.png" class="lozad post-image"></p>
<ul>
<li>
<p>1976：Xerox设计了以太网</p>
</li>
<li>
<p>70年代后期：</p>
<p>1.私有网络体系结构：DECnet，SNA，XNA</p>
<p>2.固定长度分组交换（ATM先驱）</p>
</li>
<li>
<p>1975：ARPAnet交移给美国国防部通信局管理</p>
</li>
<li>
<p>1979：ARPAnet拥有200结点</p>
</li>
</ul>
<h3 id="1980-1990新型网络协议与网络的激增"><a class="markdownIt-Anchor" href="#1980-1990新型网络协议与网络的激增"></a> 1980-1990：新型网络协议与网络的激增</h3>
<ul>
<li>
<p>1983：部署TCP/IP</p>
</li>
<li>
<p>1982：定义了SMTP电子邮件协议</p>
</li>
<li>
<p>1983：定义DNS</p>
</li>
<li>
<p>1985：定义FTP协议</p>
</li>
<li>
<p>1988：TCP拥塞控制</p>
</li>
<li>
<p>新型国家级网络：CSnet，BITnet，NSFnet，Minitel</p>
</li>
<li>
<p>1986：NSFnet初步形成了一个由骨干网、区域网和校园网组成三级网络</p>
<p>100,000台主机连接公共网络</p>
</li>
</ul>
<h3 id="1990-2000年代早期商业化web新应用"><a class="markdownIt-Anchor" href="#1990-2000年代早期商业化web新应用"></a> 1990-2000年代早期：商业化，Web，新应用</h3>
<ul>
<li>
<p>1990年代早期：ARPAnet退役</p>
</li>
<li>
<p>1991：NSF解除NSFnet的商业应用限制（1995年退役），由私营企业经营</p>
</li>
<li>
<p>1992：因特网协会ISOC成立</p>
</li>
<li>
<p>1990年代后期：Web应用</p>
<p>1.超文本</p>
<p>2.HTML，HTTP:Berners-Lee</p>
<p>3.1994:Mosaic、Netscape浏览器</p>
<p>4.1990年代后期：Web开始商业应用</p>
</li>
<li>
<p>1990年代后期-2000年代</p>
<p>1.更多及受关注的网络应用：即时消息系统（如QQ），P2P文件共享</p>
<p>2.网络安全引起重视</p>
<p>3.网络主机约达1亿以上</p>
<p>4.网络主干链路带宽达到Gbps</p>
</li>
</ul>
<h3 id="2005-今"><a class="markdownIt-Anchor" href="#2005-今"></a> 2005-今</h3>
<ul>
<li>
<p>约达到7.5亿台主机</p>
<p>1.智能手机和平板电脑</p>
</li>
<li>
<p>宽带接入的快速部署</p>
</li>
<li>
<p>无所不在的高速无线接入快速增长</p>
</li>
<li>
<p>出现在线社交网络：</p>
<p>1.Facebook：拥有10亿用户</p>
</li>
<li>
<p>服务提供商(如Google，Microsoft)创建其自己的专用网络</p>
<p>1.绕开lnternet，提供“即使”接入搜索、email等服务</p>
</li>
<li>
<p>电子商务、大学、企业等开始在“云”中运行自己的服务（如：Amazon EC2）</p>
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<ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%A6%82%E8%BF%B0"><span class="toc-number">1.</span> <span class="toc-text"> 计算机网络概述</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%9A%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.1.</span> <span class="toc-text"> 计算机网络的基本概念</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C"><span class="toc-number">1.1.1.</span> <span class="toc-text"> 什么是计算机网络？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AFlnternet"><span class="toc-number">1.1.2.</span> <span class="toc-text"> 什么是lnternet？</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%84%E6%88%90%E7%BB%86%E8%8A%82"><span class="toc-number">1.1.2.1.</span> <span class="toc-text"> 组成细节</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%9C%8D%E5%8A%A1%E8%A7%92%E5%BA%A6"><span class="toc-number">1.1.2.2.</span> <span class="toc-text"> 服务角度</span></a></li></ol></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.</span> <span class="toc-text"> 网络协议</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.1.</span> <span class="toc-text"> 什么是网络协议？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8D%8F%E8%AE%AE%E4%B8%89%E8%A6%81%E7%B4%A0"><span class="toc-number">1.2.2.</span> <span class="toc-text"> 协议三要素</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%BB%93%E6%9E%84"><span class="toc-number">1.3.</span> <span class="toc-text"> 计算机网络结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E8%BE%B9%E7%BC%98"><span class="toc-number">1.3.1.</span> <span class="toc-text"> 网络边缘</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8E%A5%E5%85%A5%E7%BD%91%E7%BB%9C"><span class="toc-number">1.3.2.</span> <span class="toc-text"> 接入网络</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E6%A0%B8%E5%BF%83"><span class="toc-number">1.3.3.</span> <span class="toc-text"> 网络核心</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.3.1.</span> <span class="toc-text"> 电路交换</span></a><ol class="toc-child"><li class="toc-item toc-level-5"><a class="toc-link" href="#%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8"><span class="toc-number">1.3.3.1.1.</span> <span class="toc-text"> 多路复用</span></a></li></ol></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8A%A5%E6%96%87%E4%BA%A4%E6%8D%A2%E4%B8%8E%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.4.</span> <span class="toc-text"> 报文交换与分组交换</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E4%B8%8E%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.5.</span> <span class="toc-text"> 分组交换与电路交换</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%80%A7%E8%83%BD"><span class="toc-number">1.4.</span> <span class="toc-text"> 计算机网络性能</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%80%9F%E7%8E%87"><span class="toc-number">1.4.1.</span> <span class="toc-text"> 速率</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%B8%A6%E5%AE%BD"><span class="toc-number">1.4.2.</span> <span class="toc-text"> 带宽</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%BB%B6%E8%BF%9F%E6%97%B6%E5%BB%B6"><span class="toc-number">1.4.3.</span> <span class="toc-text"> 延迟&#x2F;时延</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%97%B6%E5%BB%B6%E5%B8%A6%E5%AE%BD%E7%A7%AF"><span class="toc-number">1.4.4.</span> <span class="toc-text"> 时延带宽积</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%B8%A2%E5%A4%B1%E4%B8%A2%E5%8C%85"><span class="toc-number">1.4.5.</span> <span class="toc-text"> 分组丢失（丢包）</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%90%9E%E5%90%90%E9%87%8F%E7%8E%87"><span class="toc-number">1.4.6.</span> <span class="toc-text"> 吞吐量&#x2F;率</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84"><span class="toc-number">1.5.</span> <span class="toc-text"> 计算机网络体系结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E5%B1%82%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.5.1.</span> <span class="toc-text"> 分层网络体系结构基本概念</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.2.</span> <span class="toc-text"> OSI参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E8%A7%A3%E9%87%8A%E7%9A%84%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.3.</span> <span class="toc-text"> OSI参考模型解释的通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E6%95%B0%E6%8D%AE%E5%B0%81%E8%A3%85%E4%B8%8E%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.4.</span> <span class="toc-text"> OSI参考模型数据封装与通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E9%9D%9E%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.5.</span> <span class="toc-text"> OSI非端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.6.</span> <span class="toc-text"> OSI端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#tcpip%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.7.</span> <span class="toc-text"> TCP&#x2F;IP参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#5%E5%B1%82%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.8.</span> <span class="toc-text"> 5层参考模型</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E5%8F%91%E5%B1%95%E5%8E%86%E5%8F%B2"><span class="toc-number">1.6.</span> <span class="toc-text"> 计算机网络发展历史</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#1961-1972%E6%97%A9%E6%9C%9F%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E5%8E%9F%E7%90%86%E6%8F%90%E5%87%BA%E4%B8%8E%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.1.</span> <span class="toc-text"> 1961-1972：早期分组交换原理提出与应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1972-1980%E7%BD%91%E7%BB%9C%E4%BA%92%E8%81%94%E5%A4%A7%E9%87%8F%E6%96%B0%E5%9E%8B-%E7%A7%81%E6%9C%89%E7%BD%91%E7%BB%9C%E7%9A%84%E6%B6%8C%E7%8E%B0"><span class="toc-number">1.6.2.</span> <span class="toc-text"> 1972-1980：网络互联，大量新型、私有网络的涌现</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1980-1990%E6%96%B0%E5%9E%8B%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE%E4%B8%8E%E7%BD%91%E7%BB%9C%E7%9A%84%E6%BF%80%E5%A2%9E"><span class="toc-number">1.6.3.</span> <span class="toc-text"> 1980-1990：新型网络协议与网络的激增</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1990-2000%E5%B9%B4%E4%BB%A3%E6%97%A9%E6%9C%9F%E5%95%86%E4%B8%9A%E5%8C%96web%E6%96%B0%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.4.</span> <span class="toc-text"> 1990-2000年代早期：商业化，Web，新应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#2005-%E4%BB%8A"><span class="toc-number">1.6.5.</span> <span class="toc-text"> 2005-今</span></a></li></ol></li></ol></li></ol>
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<ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%A6%82%E8%BF%B0"><span class="toc-number">1.</span> <span class="toc-text"> 计算机网络概述</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%9A%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.1.</span> <span class="toc-text"> 计算机网络的基本概念</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C"><span class="toc-number">1.1.1.</span> <span class="toc-text"> 什么是计算机网络？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AFlnternet"><span class="toc-number">1.1.2.</span> <span class="toc-text"> 什么是lnternet？</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%84%E6%88%90%E7%BB%86%E8%8A%82"><span class="toc-number">1.1.2.1.</span> <span class="toc-text"> 组成细节</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%9C%8D%E5%8A%A1%E8%A7%92%E5%BA%A6"><span class="toc-number">1.1.2.2.</span> <span class="toc-text"> 服务角度</span></a></li></ol></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.</span> <span class="toc-text"> 网络协议</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.1.</span> <span class="toc-text"> 什么是网络协议？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8D%8F%E8%AE%AE%E4%B8%89%E8%A6%81%E7%B4%A0"><span class="toc-number">1.2.2.</span> <span class="toc-text"> 协议三要素</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%BB%93%E6%9E%84"><span class="toc-number">1.3.</span> <span class="toc-text"> 计算机网络结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E8%BE%B9%E7%BC%98"><span class="toc-number">1.3.1.</span> <span class="toc-text"> 网络边缘</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8E%A5%E5%85%A5%E7%BD%91%E7%BB%9C"><span class="toc-number">1.3.2.</span> <span class="toc-text"> 接入网络</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E6%A0%B8%E5%BF%83"><span class="toc-number">1.3.3.</span> <span class="toc-text"> 网络核心</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.3.1.</span> <span class="toc-text"> 电路交换</span></a><ol class="toc-child"><li class="toc-item toc-level-5"><a class="toc-link" href="#%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8"><span class="toc-number">1.3.3.1.1.</span> <span class="toc-text"> 多路复用</span></a></li></ol></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8A%A5%E6%96%87%E4%BA%A4%E6%8D%A2%E4%B8%8E%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.4.</span> <span class="toc-text"> 报文交换与分组交换</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E4%B8%8E%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.5.</span> <span class="toc-text"> 分组交换与电路交换</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%80%A7%E8%83%BD"><span class="toc-number">1.4.</span> <span class="toc-text"> 计算机网络性能</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%80%9F%E7%8E%87"><span class="toc-number">1.4.1.</span> <span class="toc-text"> 速率</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%B8%A6%E5%AE%BD"><span class="toc-number">1.4.2.</span> <span class="toc-text"> 带宽</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%BB%B6%E8%BF%9F%E6%97%B6%E5%BB%B6"><span class="toc-number">1.4.3.</span> <span class="toc-text"> 延迟&#x2F;时延</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%97%B6%E5%BB%B6%E5%B8%A6%E5%AE%BD%E7%A7%AF"><span class="toc-number">1.4.4.</span> <span class="toc-text"> 时延带宽积</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%B8%A2%E5%A4%B1%E4%B8%A2%E5%8C%85"><span class="toc-number">1.4.5.</span> <span class="toc-text"> 分组丢失（丢包）</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%90%9E%E5%90%90%E9%87%8F%E7%8E%87"><span class="toc-number">1.4.6.</span> <span class="toc-text"> 吞吐量&#x2F;率</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84"><span class="toc-number">1.5.</span> <span class="toc-text"> 计算机网络体系结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E5%B1%82%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.5.1.</span> <span class="toc-text"> 分层网络体系结构基本概念</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.2.</span> <span class="toc-text"> OSI参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E8%A7%A3%E9%87%8A%E7%9A%84%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.3.</span> <span class="toc-text"> OSI参考模型解释的通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E6%95%B0%E6%8D%AE%E5%B0%81%E8%A3%85%E4%B8%8E%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.4.</span> <span class="toc-text"> OSI参考模型数据封装与通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E9%9D%9E%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.5.</span> <span class="toc-text"> OSI非端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.6.</span> <span class="toc-text"> OSI端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#tcpip%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.7.</span> <span class="toc-text"> TCP&#x2F;IP参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#5%E5%B1%82%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.8.</span> <span class="toc-text"> 5层参考模型</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E5%8F%91%E5%B1%95%E5%8E%86%E5%8F%B2"><span class="toc-number">1.6.</span> <span class="toc-text"> 计算机网络发展历史</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#1961-1972%E6%97%A9%E6%9C%9F%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E5%8E%9F%E7%90%86%E6%8F%90%E5%87%BA%E4%B8%8E%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.1.</span> <span class="toc-text"> 1961-1972：早期分组交换原理提出与应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1972-1980%E7%BD%91%E7%BB%9C%E4%BA%92%E8%81%94%E5%A4%A7%E9%87%8F%E6%96%B0%E5%9E%8B-%E7%A7%81%E6%9C%89%E7%BD%91%E7%BB%9C%E7%9A%84%E6%B6%8C%E7%8E%B0"><span class="toc-number">1.6.2.</span> <span class="toc-text"> 1972-1980：网络互联，大量新型、私有网络的涌现</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1980-1990%E6%96%B0%E5%9E%8B%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE%E4%B8%8E%E7%BD%91%E7%BB%9C%E7%9A%84%E6%BF%80%E5%A2%9E"><span class="toc-number">1.6.3.</span> <span class="toc-text"> 1980-1990：新型网络协议与网络的激增</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1990-2000%E5%B9%B4%E4%BB%A3%E6%97%A9%E6%9C%9F%E5%95%86%E4%B8%9A%E5%8C%96web%E6%96%B0%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.4.</span> <span class="toc-text"> 1990-2000年代早期：商业化，Web，新应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#2005-%E4%BB%8A"><span class="toc-number">1.6.5.</span> <span class="toc-text"> 2005-今</span></a></li></ol></li></ol></li></ol>
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<ol class="toc"><li class="toc-item toc-level-1"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%A6%82%E8%BF%B0"><span class="toc-number">1.</span> <span class="toc-text"> 计算机网络概述</span></a><ol class="toc-child"><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%9A%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.1.</span> <span class="toc-text"> 计算机网络的基本概念</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C"><span class="toc-number">1.1.1.</span> <span class="toc-text"> 什么是计算机网络？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AFlnternet"><span class="toc-number">1.1.2.</span> <span class="toc-text"> 什么是lnternet？</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%BB%84%E6%88%90%E7%BB%86%E8%8A%82"><span class="toc-number">1.1.2.1.</span> <span class="toc-text"> 组成细节</span></a></li><li class="toc-item toc-level-4"><a class="toc-link" href="#%E6%9C%8D%E5%8A%A1%E8%A7%92%E5%BA%A6"><span class="toc-number">1.1.2.2.</span> <span class="toc-text"> 服务角度</span></a></li></ol></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.</span> <span class="toc-text"> 网络协议</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E4%BB%80%E4%B9%88%E6%98%AF%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE"><span class="toc-number">1.2.1.</span> <span class="toc-text"> 什么是网络协议？</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%8D%8F%E8%AE%AE%E4%B8%89%E8%A6%81%E7%B4%A0"><span class="toc-number">1.2.2.</span> <span class="toc-text"> 协议三要素</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E7%BB%93%E6%9E%84"><span class="toc-number">1.3.</span> <span class="toc-text"> 计算机网络结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E8%BE%B9%E7%BC%98"><span class="toc-number">1.3.1.</span> <span class="toc-text"> 网络边缘</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8E%A5%E5%85%A5%E7%BD%91%E7%BB%9C"><span class="toc-number">1.3.2.</span> <span class="toc-text"> 接入网络</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E7%BD%91%E7%BB%9C%E6%A0%B8%E5%BF%83"><span class="toc-number">1.3.3.</span> <span class="toc-text"> 网络核心</span></a><ol class="toc-child"><li class="toc-item toc-level-4"><a class="toc-link" href="#%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.3.1.</span> <span class="toc-text"> 电路交换</span></a><ol class="toc-child"><li class="toc-item toc-level-5"><a class="toc-link" href="#%E5%A4%9A%E8%B7%AF%E5%A4%8D%E7%94%A8"><span class="toc-number">1.3.3.1.1.</span> <span class="toc-text"> 多路复用</span></a></li></ol></li></ol></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%8A%A5%E6%96%87%E4%BA%A4%E6%8D%A2%E4%B8%8E%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.4.</span> <span class="toc-text"> 报文交换与分组交换</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E4%B8%8E%E7%94%B5%E8%B7%AF%E4%BA%A4%E6%8D%A2"><span class="toc-number">1.3.5.</span> <span class="toc-text"> 分组交换与电路交换</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E6%80%A7%E8%83%BD"><span class="toc-number">1.4.</span> <span class="toc-text"> 计算机网络性能</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E9%80%9F%E7%8E%87"><span class="toc-number">1.4.1.</span> <span class="toc-text"> 速率</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%B8%A6%E5%AE%BD"><span class="toc-number">1.4.2.</span> <span class="toc-text"> 带宽</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%BB%B6%E8%BF%9F%E6%97%B6%E5%BB%B6"><span class="toc-number">1.4.3.</span> <span class="toc-text"> 延迟&#x2F;时延</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E6%97%B6%E5%BB%B6%E5%B8%A6%E5%AE%BD%E7%A7%AF"><span class="toc-number">1.4.4.</span> <span class="toc-text"> 时延带宽积</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E7%BB%84%E4%B8%A2%E5%A4%B1%E4%B8%A2%E5%8C%85"><span class="toc-number">1.4.5.</span> <span class="toc-text"> 分组丢失（丢包）</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%90%9E%E5%90%90%E9%87%8F%E7%8E%87"><span class="toc-number">1.4.6.</span> <span class="toc-text"> 吞吐量&#x2F;率</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84"><span class="toc-number">1.5.</span> <span class="toc-text"> 计算机网络体系结构</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#%E5%88%86%E5%B1%82%E7%BD%91%E7%BB%9C%E4%BD%93%E7%B3%BB%E7%BB%93%E6%9E%84%E5%9F%BA%E6%9C%AC%E6%A6%82%E5%BF%B5"><span class="toc-number">1.5.1.</span> <span class="toc-text"> 分层网络体系结构基本概念</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.2.</span> <span class="toc-text"> OSI参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E8%A7%A3%E9%87%8A%E7%9A%84%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.3.</span> <span class="toc-text"> OSI参考模型解释的通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B%E6%95%B0%E6%8D%AE%E5%B0%81%E8%A3%85%E4%B8%8E%E9%80%9A%E4%BF%A1%E8%BF%87%E7%A8%8B"><span class="toc-number">1.5.4.</span> <span class="toc-text"> OSI参考模型数据封装与通信过程</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E9%9D%9E%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.5.</span> <span class="toc-text"> OSI非端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#osi%E7%AB%AF%E5%88%B0%E7%AB%AF%E5%B1%82%E6%AC%A1%E7%9A%84%E4%B8%BB%E8%A6%81%E5%8A%9F%E8%83%BD"><span class="toc-number">1.5.6.</span> <span class="toc-text"> OSI端到端层次的主要功能</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#tcpip%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.7.</span> <span class="toc-text"> TCP&#x2F;IP参考模型</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#5%E5%B1%82%E5%8F%82%E8%80%83%E6%A8%A1%E5%9E%8B"><span class="toc-number">1.5.8.</span> <span class="toc-text"> 5层参考模型</span></a></li></ol></li><li class="toc-item toc-level-2"><a class="toc-link" href="#%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C%E5%8F%91%E5%B1%95%E5%8E%86%E5%8F%B2"><span class="toc-number">1.6.</span> <span class="toc-text"> 计算机网络发展历史</span></a><ol class="toc-child"><li class="toc-item toc-level-3"><a class="toc-link" href="#1961-1972%E6%97%A9%E6%9C%9F%E5%88%86%E7%BB%84%E4%BA%A4%E6%8D%A2%E5%8E%9F%E7%90%86%E6%8F%90%E5%87%BA%E4%B8%8E%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.1.</span> <span class="toc-text"> 1961-1972：早期分组交换原理提出与应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1972-1980%E7%BD%91%E7%BB%9C%E4%BA%92%E8%81%94%E5%A4%A7%E9%87%8F%E6%96%B0%E5%9E%8B-%E7%A7%81%E6%9C%89%E7%BD%91%E7%BB%9C%E7%9A%84%E6%B6%8C%E7%8E%B0"><span class="toc-number">1.6.2.</span> <span class="toc-text"> 1972-1980：网络互联，大量新型、私有网络的涌现</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1980-1990%E6%96%B0%E5%9E%8B%E7%BD%91%E7%BB%9C%E5%8D%8F%E8%AE%AE%E4%B8%8E%E7%BD%91%E7%BB%9C%E7%9A%84%E6%BF%80%E5%A2%9E"><span class="toc-number">1.6.3.</span> <span class="toc-text"> 1980-1990：新型网络协议与网络的激增</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#1990-2000%E5%B9%B4%E4%BB%A3%E6%97%A9%E6%9C%9F%E5%95%86%E4%B8%9A%E5%8C%96web%E6%96%B0%E5%BA%94%E7%94%A8"><span class="toc-number">1.6.4.</span> <span class="toc-text"> 1990-2000年代早期：商业化，Web，新应用</span></a></li><li class="toc-item toc-level-3"><a class="toc-link" href="#2005-%E4%BB%8A"><span class="toc-number">1.6.5.</span> <span class="toc-text"> 2005-今</span></a></li></ol></li></ol></li></ol>
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